Field of the Invention
The present invention relates to a cleanerless image forming apparatus. More particularly, the present invention relates to a so-called cleanerless type image forming apparatus, in which a developing device is configured to develop an image bearing member with toner, and to simultaneously clean a surface of the image bearing member after transfer by removing the toner remaining on the surface of the image bearing member to reuse the toner (simultaneous development and cleaning).
Description of the Related Art
In Japanese Patent Application Laid-Open No. 559-133573, there is disclosed a cleanerless type image forming apparatus, in which a developing means develops the photosensitive drum with toner and simultaneously cleans a surface of the photosensitive drum, removes and collects transfer residual toner remaining on the surface of the photosensitive drum to reuse the transfer residual toner (simultaneous development and cleaning). In this way, the toner remaining after transfer on the surface of the photosensitive drum does not become waste toner, thereby achieving environmental protection, effective use of resources, and apparatus downsizing.
In image forming apparatus employing a cleanerless system, a part of toner charged to an opposite polarity is attracted to a contact charging member to degrade charging performance of the contact charging member. According to Japanese Patent No. 3030188, toner that is charged to an opposite polarity and attracted to a contact charger is electrostatically attracted to a photosensitive member, reversed to have a normal polarity through slide friction with a developing roller, and collected to the developing roller.
Toner sometimes cannot be reversed to have a normal polarity through the slide friction with the developing roller depending on a use environment of an image forming apparatus and a state of a developing device serving as a developing means. Further, so-called fogging which causes toner to be transferred to a photosensitive drum as a result of contact between a developing device and the photosensitive drum often occurs. Particularly in a state with worsened fogging, attraction of toner to a charging roller occurs even through contact between the developing device and the photosensitive drum. The charging roller is also required to be cleaned at appropriate timings.